Shoniqua: This is a poor conspiracy theory at best.

Given the tight margins in publishing math texts, it's my experience that any but the top .01% actually make any real profit for the authors. Given my experience the vast majority of math textbook authors actually want to give away the answers and actually help students. in the past several years, I've directly emailed math professors who've written textbooks for help and advice and most of them have actually replied, not only promptly, but typically with more information that I requested about particular problems and often with full solutions, and in many cases they've sent met full sets of solutions for their entire texts and in a few other cases, they've sent me full electronic copies of their texts for free!

I'll also note, there's also been a growing trend for mathematicians to reserve the right to publish electronic copies of their books on their personal websites where they make them freely available to students.